I'm only 10 turns into my first CoS campaign on Vortex and I'm absolutely loving it. (Some bad weather knocked out my internet for a few days so I just downloaded the DLC last night.)
I'm really enjoying the increased difficulty by only having access to skink units, and having to fight literal hoards of Skaven early. I was shocked at how many troops Clan Fester started with, including Rat Ogres no less. Something that has really stuck out to me is that because I was so outnumbered and only able to use relatively weak early units, I've actually had to think and fight more tactically than I normally do as the LM. No Saurus means no meat grinder infantry fight and I'm greatly enjoying the difference in play style.
I've even pulled off two ambushes against Clan Fester allowing me to win battles I would have no chance in otherwise. To me this is a big deal because I don't think I've ever once used the ambush stance for any reason, now I wouldn't be surviving without it.
The Red Crested Skinks are surprisingly durable in melee, though they are definitely vulnerable in prolonged fights. I haven't gotten to use all the other units yet, but I really, really, really enjoy the Ark of Sotek which I've combined with the Jungle Swarm ability for some nasty aoe effects. The swarm ability is incredibly useful against all the annoying Skaven skirmishers that are hard to catch even with skinks.
I quite like the Salamanders as well, and they average about 100 kills per battle for me, though man are they made of paper. They go down quick in melee if they get caught. I just wanted to post this in the hopes that the goodwill and enjoyment I'm getting from just one part of the DLC/FLC combo that CA picks up on it and delivers something of this quality again!